Endophytic fungi affect growth of perennial ryegrass

Abstract Clones of Lolium perenne L. ‘Grasslands Nui’ perennial ryegrass, either infected with or free from Acremonium loliae Latch, Christensen & Samuels, and clones of ‘Grasslands Ruanui’ perennial ryegrass, either infected with or free from a Gliocladium ‐like endophyte, were grown at 20°C for 8 weeks in a controlled‐environment room. Nui plants infected with A. loliae yielded 38% more total dry matter than uninfected plants. Infected plants showed significant increases in total leaf area, tiller numbers, and growth of leaves, pseudo stems, and roots, but the shoot: root ratio was unaffected. Infection of Ruanui with the Gliocladium ‐like sp. had no significant effect on yield even though total leaf area was reduced by 19%. The benefits in yield and protection from damage by Argentine stem weevil from A. loliae ‐infected ryegrasses are discussed in relation to the known risk of ill‐health in animals grazing infected pastures.